Optimize roll operator in CPDF_PSEngine.

core/fpdfapi/page/fpdf_page_func.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fpdfapi/page/pageint.h"
 
 #include <limits.h>
 
@@ skipping 358 matching lines @@
     case PSOP_INDEX: {
       int n = static_cast<int>(Pop());
       if (n < 0 || n >= static_cast<int>(m_StackCount))
         break;
       Push(m_Stack[m_StackCount - n - 1]);
       break;
     }
     case PSOP_ROLL: {
       int j = static_cast<int>(Pop());
       int n = static_cast<int>(Pop());
-      if (m_StackCount == 0)
+      if (j == 0 || n == 0 || m_StackCount == 0)
         break;
       if (n < 0 || n > static_cast<int>(m_StackCount))
         break;
+
+      j %= n;
       if (j < 0) {
         for (int i = 0; i < -j; i++) {
           FX_FLOAT first = m_Stack[m_StackCount - n];
           for (int ii = 0; ii < n - 1; ii++)
             m_Stack[m_StackCount - n + ii] = m_Stack[m_StackCount - n + ii + 1];
           m_Stack[m_StackCount - 1] = first;
         }
       } else {
         for (int i = 0; i < j; i++) {
           FX_FLOAT last = m_Stack[m_StackCount - 1];
@@ skipping 443 matching lines @@
   return m_Type == Type::kType2ExpotentialInterpolation
              ? static_cast<const CPDF_ExpIntFunc*>(this)
              : nullptr;
 }
 
 const CPDF_StitchFunc* CPDF_Function::ToStitchFunc() const {
   return m_Type == Type::kType3Stitching
              ? static_cast<const CPDF_StitchFunc*>(this)
              : nullptr;
 }